1. Field of the Invention
The invention relates to the treatment by an ultrasonic focussed beam of anatomical anomalies and, more particularly, of shallow structures for which the focal spot of the beam must be relatively fine.
2. Description of the Prior Art
The French patent 84 06877 describes a hyperthermia device using a power transducer in the form of a spherical cup which generates ultrasonic wave trains, having for example frequencies of the order of 500 kHz. The location of the anatomical target and observation thereof during firing takes place by means of an auxiliary transducer mechanically coupled to the cup and excited by an echographic pulse generator having, for example, a frequency of 5 MHz.
This device is adapted for the treatment of deep tissues, the 500 KHz frequency waves being relatively little absorbed during their propagation through the tissues. Considering its size (diameter of 200 to 300 mm for example) the cup is not capable of being subjected to rapid movement which would permit echographic scanning in real time and, in any case, its operating frequency would not be adapted to the formation of good quality echographic images.
The published Japanese patent application 58 188431 has in particular proposed using the power transducer alternately for the treatment and for the echography. When such a principle is used with a fixed power transducer, either a type A echography is carried out, which only delivers indications of the distance of the target or else scanning by the echographic beam is generated by excitation of the transducer with waves which are phase-shifted with respect to each other. This latter solution is complicated and does not provide scanning of the target in a sufficient angle. Furthermore, this principle does not make it possible to observe the target during the treatment sequence.